Fourdrinier wires for paper machines



July 14, 1964' H. JOHNSON FOURDRINIER WIRES FOR PAPER MACHINES Filed June 19, 1961 INVENTOR HENRY JOHNSON ATmR/wsys United States Patent T 3,140,973 FOURDRINIER WIRES FOR PAPER MACHINES Henry Johnson, 530 De Courcelle St., Montreal 30, Quebec, Canada Filed June 19, 1961, Ser. No. 118,127 6 Claims. (Cl. 161-92) This invention relates to improvements in Fourdrinier wires for paper machines and particularly to such improvements as will contribute to the elimination of wire marks on the forming sheet of paper.

The wire marks transmitted to the sheet of paper as it is formed on the Fourdrinier wire of the machine, and particularly on newsprint paper, results from the wet pulp being moulded into the crevices at the cross-over of the warp and weft strands of the Fourdrinier wire. These wire marks are partially smoothed out by the press rolls of the paper machine, but not entirely so. The wire marks result in minute depressions over the whole surface of the finished paper sheet, particularly on the side of the paper which has been in contact with the Fourdrinier wire. Thus, when the sheet is printed on, and particularly in the printing of photographs, the ink will not flow into these minute depressions with the result that the printing will become blurred. A close examination of the printing on opposite sides of a sheet will reveal that the printing on the side of the sheet which has been in contact with the Fourdrinier wire is considerably more blurred than the printing on the side of the sheet which was not in direct contact with the Fourdrinier wire.

The present invention has for its object the formation of a monoplane surface along the lines of the warp and weft strands of the wire. This may be effected on the paper carrying surface of the wire or it may be efiected on both surfaces of the wire. In addition, the invention can be applied to any type of weave of the wire. The invention is accomplished by applying a plastic material to the Fourdrinier wire in such a manner that the plastic material will adhere to the surface of the warp and weft strands of the wire and will fill in the depressions at the cross-over of the strands and between the knuckles of the strands to the level of the outer longitudinal surface plane of the wire. The plastic material will be applied to the wire in such a manner that the drainage openings in the wire are not reduced in area. The application of the plastic material is preferably carried out by spraying one or both surfaces of the wire and the drainage openings are kept free of plastic by passing hot air through the wire while the plastic is still hot and pliable.

The invention is illustrated in the accompany drawings, in which:

FIG. 1 is an enlarged plan view of a section of Fourdrinier wire showing the plastic material applied to the warp and weft strands to fill in the depressions at the cross-over of the wires.

FIG. 2 is a vertical cross section on the lines 2-2 of FIG. 1.

FIG. 3 is an enlarged vertical cross section on the line 33 of FIG. 2.

FIG. 4 is a vertical cross section similar to FIG. 2 but showing the plastic material applied on both surfaces of the wire.

FIG. 5 is an enlarged vertical cross section on the line 5-5 of FIG. 4.

FIG. 6 is similar to FIG. 3 but showing a flat top surface to the plastic.

Referring to the drawings, the Fourdrinier wire is woven in any desired type of weave, either plain or twill, and is here shown as being woven with a twill weave of which the warp strands are indicated by the numeral 5 and the weft strands by the numeral 6.

As seen in FIGS, 1, 2 and 3, the plastic material is 3,140,973 Patented July 14, 1964 applied to the paper supporting side 7 of the wire in such a manner that the depressions between the knuckles 8 of the warp strands 5 and the knuckles 9 of the weft strands 6 at each cross-over of the strands is filled up by the indi vidual deposits 10 of the plastic material. Each of the individual deposits 10 of the plastic is the same width as the diameter of the wire strand at the point of crossover of the wires and taper off towards the crest of the knuckles of the strands and are preferably rounded 01f at their top surface 11 as shown in FIG. 3 so as to assist in the free flow of the water through the drainage openings 12 of the wire. During the application of the plastic material to the surface of the strands, preferably by spraying, there will be a tendency for the plastic to adhere to the surfaces of the warp and weft strands defining the depressions between the knuckles of the strands and, because of the downward slope of the surface of any one strand from the crest of the knuckle to the point of cross-over of the adjacent strand, the soft and pliable plastic will tend to build up vertically in the depression against the surface of the said adjacent cross-over strand, and across the full width of the crossed-over strand. The build-up of the plastic in the depression will also tend to taper-off, from the full width of the strands at the bottom of the depression at the point of cross-over of the strands, inwardly towards the vertical plane passing through the axis of the strands, and in the direction of the crest of the knuckles of the strands in the manner shown in FIG. 1. Any buildup of the plastic medium above the longitudinal surface plane of the wire can be removed by a wiping action while the plastic is still hot and pliable. Such wiping action will tend to flatten the top surface of the deposits of plastic as shown at 13 in FIG. 6. Flattening can also be accomplished by rolling or grinding. Such flattening of the top surface of the finished wire will provide a greater area of support for the pulp fibres without reducing the area of the drainage openings 12. The volume of plastic deposited can be restricted in well known manner such as by spraying the woven wire with plastic and then passing hot air through the mesh while the plastic is still hot and pliable, in order that the drainage openings will not be restricted.

In FIGS. 4 and 5 the plastic material is shown applied to both surfaces of the Fourdrinier wire. In this case the top surfaces of the strands 5 and 6 are covered by the individual deposits 14 of plastic and the bottom surfaces by the individual deposits 15. These individual deposits 14 and 15 may or may not meet at the longitudinal axis of the strands at 16. Plastic materials which are considered satisfactory for the carrying out of this invention include epoxy-phenolic, epoXy-polyamide, catalyzed epoxy, polyvinyl butyral wash primer with a vinyl chloride-vinyle acetate copolymer topcoat, urea alkyd over polyvinyl butyral wash primer, butoxy, polyurethane and epoxy-ester. These plastic materials, after being applied to the wire mesh, are cured by baking in an oven at from 375 F. to 425 F. The time required to effect curing of the plastic material is from ten to fifteen minutes depending on the specific plastic used.

By filling in the crevices at the cross-over of the warp and weft strands with a deposit of plastic material, a monoplane surface is created along each strand which will hold the fibres of the wet pulp to the plane of the paper carrying surface of the Fourdrinier wire without reducing the area of the drainage openings in the wire. The plastic deposits, by preventing the wet pulp from falling into the crevices at the cross-over of the wire strands will thereby eliminate the minute depressions in the finished paper and so provide a smoother and better inking surface.

Furthermore, by filling in the crevices at the cross-over of the wire strands there will be a tendency for less turbulence in the Water drawn through the Wire and 3 therefore less disturbance in the lay of the fibres of the pulp with consequent improvement in the quality of the formed sheet of paper.

When a printed impression is made on both surfaces of the improved paper sheet formed on a Fourdrinier wire of the type described above, the printed impression will have the same degree of clarity on both sides of the sheet, and will be particularly noticeable in the printing of photographs on newsprint paper.

What I claim is:

1. In a Fourdrinier wire formed of woven warp and Weft strands which combine to form a series of depressions under the longitudinal surface plane of the woven Wire, the said depressions being defined by the crests of the knuckles of the Warp and weft strands at their point of cross-over with each other, a plastic material filling applied to each of said depressions in the woven wire, the said fillings of plastic material having a Width not greater than the diameter of each individual wire strand and extending along the surface of the individual warp and weft strands from the crest of the knuckle of one strand to the crest of the knuckle of the adjacent cross-over strands to fill the said depressions, the said fillings extending vertically from the surface of the strands to the level of the longitudinal surface plane of the Fourdrinier wire as defined 4 by the crests of the knuckles of the individual warp and Weft strands.

2. In a Fourdrinier wire as set forth in claim 1, in which the said filling fills the depressions on both surfaces of the wire.

3. In a Fourdrinier Wire as set forth in claim 1, in which the surface of the filling adjacent the longitudinal surface plane of the wire is rounded.

4. In a Fourdrinier wire as set forth in claim 1, in which the surface of the filling is made level with the adjacent longitudinal plane of the wire.

5. In a Fourdrinier wire as set forth in claim 1, in which the individual fillings extend along the longitudinal axis of the warp and weft strands to blend with the adjacent fillings at the longitudinal surface plane of the wire.

6. In a Fourdrinier wire as set forth in claim 1, in which the fillings fill the depressions on the paper forming surface of the wire.

References Cited in the file of this patent UNITED STATES PATENTS 1,934,643 Rafton Nov. 7, 1933 2,050,156 Borghetty Aug. 4, 1936 2,777,779 Harwood et al Jan. 15, 1957 2,874,729 Ball Feb. 24, 1959 

1. IN A FOURDRINIER WIRE FORMED OF WOVEN WARP AND WEFT STRANDS WHICH COMBINE TO FORM A SERIES OF DEPRESSIONS UNDER THE LONGITUDINAL SURFACE PLANE OF THE WOVEN WIRE, THE SAID DEPRESSIONS BEING DEFINED BY THE CRESTS OF THE KNUCKLES OF THE WARP AND WEFT STRANDS AT THEIR POINT OF CROSS-OVER WITH EACH OTHER, A PLASTIC MATERIAL FILLING APPLIED TO EACH OF SAID DEPRESSIONS IN THE WOVEN WIRE, THE SAID FILLINGS OF PLASTIC MATERIAL HAVING A WIDTH NOT GREATER THAN THE DIAMETER OF EACH INDIVIDUAL WIRE STRAND AND EXTENDING ALONG THE SURFACE OF THE INDIVIUAL WARP AND WEFT STRANDS FROM THE CREST OF THE KNUCKLE OF ONE STRAND TO THE CREST OF THE KNUCKLE OF THE ADJACENT CROSS-OVER STRANDS TO FILL THE SAID DEPRESSIONS, THE SAID FILLINGS EXTENDING VERTICALLY FROM THE SURFACE OF THE STRANDS TO THE LEVEL OF THE LONGITUDINAL SURFACE PLANE OF THE FOURDRINIER WIRE AS DEFINED BY THE CRESTS OF THE KNUCKLES OF THE INDIVIDUAL WARP AND WEFT STRANDS. 